example: Add handling specific service Error code (aws#862)

Adds example which shows how specific service error codes can be handled.

example/aws/request/handleServiceErrorCodes/README.md

@@ -0,0 +1,17 @@
+# Handling Specific Service Error Codes
+
+This examples highlights how you can use the `awserr.Error` type to perform logic based on specific error codes returned by service API operations.
+
+In this example the `S3` `GetObject` API operation is used to request the contents of a object in S3. The example handles the `NoSuchBucket` and `NoSuchKey` error codes printing custom messages to stderr. If Any other error is received a generic message is printed.
+
+## Usage
+
+Will make a request to S3 for the contents of an object. If the request was successful, and the object was found the object's path and size will be printed to stdout.
+
+If the object's bucket or key does not exist a specific error message will be printed to stderr for the error.
+
+Any other error will be printed as an unknown error.
+
+```sh
+go run handleServiceErrorCodes.go mybucket mykey
+```

example/aws/request/handleServiceErrorCodes/handleServiceErrorCodes.go

@@ -0,0 +1,67 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/awserr"
+	"github.com/aws/aws-sdk-go/aws/session"
+	"github.com/aws/aws-sdk-go/service/s3"
+)
+
+func exitErrorf(msg string, args ...interface{}) {
+	fmt.Fprintf(os.Stderr, msg+"\n", args...)
+	os.Exit(1)
+}
+
+// Will make a request to S3 for the contents of an object. If the request
+// was successful, and the object was found the object's path and size will be
+// printed to stdout.
+//
+// If the object's bucket or key does not exist a specific error message will
+// be printed to stderr for the error.
+//
+// Any other error will be printed as an unknown error.
+//
+// Usage: handleServiceErrorCodes <bucket> <key>
+func main() {
+	if len(os.Args) < 3 {
+		exitErrorf("Usage: %s <bucket> <key>", filepath.Base(os.Args[0]))
+	}
+	sess, err := session.NewSession()
+	if err != nil {
+		exitErrorf("failed to create session,", err)
+	}
+
+	svc := s3.New(sess)
+	resp, err := svc.GetObject(&s3.GetObjectInput{
+		Bucket: aws.String(os.Args[1]),
+		Key:    aws.String(os.Args[2]),
+	})
+
+	if err != nil {
+		// Casting to the awserr.Error type will allow you to inspect the error
+		// code returned by the service in code. The error code can be used
+		// to switch on context specific functionality. In this case a context
+		// specific error message is printed to the user based on the bucket
+		// and key existing.
+		//
+		// For information on other S3 API error codes see:
+		// http://docs.aws.amazon.com/AmazonS3/latest/API/ErrorResponses.html
+		if aerr, ok := err.(awserr.Error); ok {
+			switch aerr.Code() {
+			case "NoSuchBucket":
+				exitErrorf("bucket %s does not exist", os.Args[1])
+			case "NoSuchKey":
+				exitErrorf("object with key %s does not exist in bucket %s", os.Args[2], os.Args[1])
+			}
+		}
+		exitErrorf("unknown error occured, %v", err)
+	}
+	defer resp.Body.Close()
+
+	fmt.Printf("s3://%s/%s exists. size: %d\n", os.Args[1], os.Args[2],
+		aws.Int64Value(resp.ContentLength))
+}